Filtering of spin currents based on ballistic ring

TL;DR

This paper investigates how quantum interference in ballistic rings with spin-orbit interactions can be used to control and generate spin-polarized currents from unpolarized inputs, highlighting the role of disorder and spin splitting.

Contribution

It provides an analytical study of spin-dependent transport in a ballistic ring considering natural spin-orbit interactions and demonstrates spin current filtering and polarization effects.

Findings

Spin-dependent current oscillations due to spin splitting.

Unpolarized current can be converted into spin-polarized current.

Disorder influences spin current behavior and filtering efficiency.

Abstract

Quantum interference effects in rings provide suitable means for controlling spin at mesoscopic scales. Here we apply such a control mechanism to the spin-dependent transport in a ballistic quasi one dimensional ring patterned in two dimensional electron gases (2DEGs). The study is essentially based on the {\it natural} spin-orbit (SO) interactions, one arising from the laterally confining electric field {($\beta$ term) and the other due to to the quantum-well potential that confines electrons in the 2DEG (conventional Rashba SO interaction or $\alpha$ term).} We focus on single-channel transport and solve analytically the spin polarization of the current. As an important consequence of the presence of spin splitting, we find the occurrence of spin dependent current oscillations. We analyze %the effects of disorder by discussing the transport in the presence of one non-magnetic obstacle in the ring. We demonstrate that a spin polarized current can be induced when an unpolarized charge current is injected in the ring, by focusing on the central role that the presence of the obstacle plays.